Depth interactions and reproductive ecology of sympatric Sillaginidae: Sillago robusta and S. flindersi

Ca Gray,Wd Robbins,Fa Ochwada-Doyle,Lm Barnes,Bw Kendall,De Van Der Meulen

doi:10.3354/ab00578

Abstract

This study examined whether differences existed in the depth distributions and reproductive strategies of the co-occurring Sillago robusta and S. flindersi in coastal waters off eastern Australia. Marked spatial and temporal dissimilarities in demography and reproduction were observed between the 2 species, with S. robusta being more abundant in the shallow (15�30 m) strata and S. flindersi in the mid (31�60 m) strata, with neither species being consis- tently abundant in the deep (61�90 m) strata. The size composition of S. robusta was similar across depths, but smaller and immature S. flindersi predominantly occurred in the shallow strata, with larger and mature individuals occurring deeper. These data indicate partitioning of habitat resources, which may aid species coexistence. Both species potentially spawned year-round, which is probably an adaptation to the region's dynamic coastal environment. However, a greater proportion of S. robusta was in spawning condition between September and March, whereas S. flindersi displayed no such temporal pattern. Maturity ogives differed significantly between sexes and locations for both species. Both species displayed similar ovarian development, with females having multiple concurrent oocyte stages, indicating potential multiple spawning events as evidenced in other Sillaginidae. For both species, estimated batch fecundity increased with fish length, but S. robusta had a greater fecundity at any given length than S. flindersi. In contrast, S. flindersi potentially produced larger-sized eggs and invested greater energy into gonad devel- opment than S. robusta, indicating the 2 species have evolved slightly different reproductive strategies. Despite this, both species are subjected to substantial trawl fisheries, which may have already impacted their reproductive ecologies.

Highlights

Knowledge of the life history characteristics of cooccurring species is fundamental to understanding biotic processes that influence structure and maintenance of assemblages of organisms (Schoener 1974, Ross 1986, Roff 1992)
Gray et al.: Reproductive strategies of sympatric Sillaginidae and display depth-associated ontogenetic shifts in distribution that may assist partitioning of resources (Burchmore et al 1988, Hyndes et al 1996a,b, 1997, Kendall & Gray 2009). We investigate whether this general paradigm is applicable to S. robusta and S. flindersi where their distributions overlap in coastal waters off eastern Australia
The General linear models (GLMs) showed that depth and season influenced the relative abundance of Sillago robusta and S. flindersi in different ways

Summary

Introduction

Knowledge of the life history characteristics of cooccurring species is fundamental to understanding biotic processes that influence structure and maintenance of assemblages of organisms (Schoener 1974, Ross 1986, Roff 1992). Related teleost species that coexist often display different life history characteristics, such as reproductive and recruitment strategies, diets and small-scale distributions and abundances (Ross 1977, Roff 1991, Hyndes et al 1997, Genner et al 1999, Colloca et al 2010). Several species are important in commercial, recreational and artisanal fisheries (McKay 1992, Kailola et al 1993, Gray & Kennelly 2003)

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Results

Conclusion